How to calculate Charge Pump output current capacity of TPS65150?

Hallo Kevin,

This answer refers to the latest revision of the TPS65150 data sheet (SLVS576A).

The short answer is that there should be no problem getting 25 mA from each charge pump, and with a bit more care you should be able to get 50 mA.

Below is the long answer.

In the negative charge pump there is a current sink called IDRVN, and in the positive charge pump there is a current source called IDRVP. You can see these clearly in Figure 10 and Figure 11 of the TPS65150 data sheet (see example below). The output current from this current sink and current source is variable, and the TPS65150 continuously adjusts IDRVN and IDRVP so that the charge pumps' output voltages are correct.

The maximum output current that the charge pumps can generate occurs when IDRVN and IDRVP have been adjusted to their maximum value. When this happens:

• The positive charge pump output current = IDRVP(max)/2
• The negative charge pump current = IDRVN(max)/2

The output current is only half IDRVN and half IDRVP because the charge pumps operate with a 50% duty cycle.

Most of our products that have charge pumps specify a value for IDRVN(max) and IDRVP(max) in the data sheet. Unfortunately, the TPS65150 data sheet does not include this information (I don't know why not). But the TPS65150 data sheet does specify the voltage drop across the internal current sink/source at 100 mA, so we can assume that IDRVN(max) and IDRVP(max) are at least 100 mA, which means a maximum output current from the charge pumps of 50 mA.

Note that most of the application circuits in the TPS65150 data sheet are designed for output currents of 20 mA. If you want to generate larger output currents, you may need to use a larger flying capacitor (CFLY in the above block diagram).